| |
| //===------------ MIRVRegNamerUtils.h - MIR VReg Renaming Utilities -------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // The purpose of these utilities is to abstract out parts of the MIRCanon pass |
| // that are responsible for renaming virtual registers with the purpose of |
| // sharing code with a MIRVRegNamer pass that could be the analog of the |
| // opt -instnamer pass. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_LIB_CODEGEN_MIRVREGNAMERUTILS_H |
| #define LLVM_LIB_CODEGEN_MIRVREGNAMERUTILS_H |
| |
| #include "llvm/ADT/PostOrderIterator.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| #include <queue> |
| |
| namespace llvm { |
| |
| /// NamedVRegCursor - The cursor is an object that keeps track of what the next |
| /// vreg name should be. It does book keeping to determine when to skip the |
| /// index value and by how much, or if the next vreg name should be an increment |
| /// from the previous. |
| class NamedVRegCursor { |
| MachineRegisterInfo &MRI; |
| |
| /// virtualVRegNumber - Book keeping of the last vreg position. |
| unsigned virtualVRegNumber; |
| |
| /// SkipGapSize - Used to calculate a modulo amount to skip by after every |
| /// sequence of instructions starting from a given side-effecting |
| /// MachineInstruction for a given MachineBasicBlock. The general idea is that |
| /// for a given program compiled with two different opt pipelines, there |
| /// shouldn't be greater than SkipGapSize difference in how many vregs are in |
| /// play between the two and for every def-use graph of vregs we rename we |
| /// will round up to the next SkipGapSize'th number so that we have a high |
| /// change of landing on the same name for two given matching side-effects |
| /// for the two compilation outcomes. |
| const unsigned SkipGapSize; |
| |
| /// RenamedInOtherBB - VRegs that we already renamed: ie breadcrumbs. |
| std::vector<Register> RenamedInOtherBB; |
| |
| public: |
| NamedVRegCursor() = delete; |
| /// 1000 for the SkipGapSize was a good heuristic at the time of the writing |
| /// of the MIRCanonicalizerPass. Adjust as needed. |
| NamedVRegCursor(MachineRegisterInfo &MRI, unsigned SkipGapSize = 1000) |
| : MRI(MRI), virtualVRegNumber(0), SkipGapSize(SkipGapSize) {} |
| |
| /// SkipGapSize - Skips modulo a gap value of indices. Indices are used to |
| /// produce the next vreg name. |
| void skipVRegs(); |
| |
| unsigned getVirtualVReg() const { return virtualVRegNumber; } |
| |
| /// incrementVirtualVReg - This increments an index value that us used to |
| /// create a new vreg name. This is not a Register. |
| unsigned incrementVirtualVReg(unsigned incr = 1) { |
| virtualVRegNumber += incr; |
| return virtualVRegNumber; |
| } |
| |
| /// createVirtualRegister - Given an existing vreg, create a named vreg to |
| /// take its place. |
| unsigned createVirtualRegister(unsigned VReg); |
| |
| /// renameVRegs - For a given MachineBasicBlock, scan for side-effecting |
| /// instructions, walk the def-use from each side-effecting root (in sorted |
| /// root order) and rename the encountered vregs in the def-use graph in a |
| /// canonical ordering. This method maintains book keeping for which vregs |
| /// were already renamed in RenamedInOtherBB. |
| // @return changed |
| bool renameVRegs(MachineBasicBlock *MBB); |
| }; |
| |
| } // namespace llvm |
| |
| #endif |